We will evaluate possible early neurogenic influences in essential hypertension (EH) by monitoring heart growth in a biracial sample of 200 Baltimore adolescents over a 2-year interval. The goal is to test 2 different models of sympathetic nervous system (SNS) influence on the early pathophysiology of EH. The first neurogenic model envisages a primary SNS abnormality in the form of excessive BP reactivity to stress eventually causing vascular changes that produce sustained EH. We will evaluate this by determining if an excessively variable or reactive BP in Study Year 1 (controlling for BP level) heralds the appearance of excessive heart growth or left ventricular hypertrophy (LVH) over the 2-year follow-up. The second model considers the fundamental abnormality to involve chronically elevated SNS drive to the heart. We will determine if a tendency to hyperkinetic circulation and higher prevailing BP exacerbated by personality, stress, and dietary sodium lead to increase LVH at follow-up. A battery of cardiovascular, behavioral and anthropometric measures will be administered at school and during a clinic visit at Baseline and at 12-month and 24-month follow-up. Structural equation modeling will be used to evaluate a model of heart growth as a function of changes in body size and composition, maturation, and physical fitness. We will then ascertain the ability of each neurogenic model to account for the residual variance in ventricular growth not explained by our "normal physical development" model. In the final phase of the analysis, the possible interaction of SNS and maturational influences will be considered.